This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/JP00/08140 which has an International filing date of Nov. 20, 2000, which designated the United States of America.
The present invention relates to a refrigeration system which uses a working medium containing an R32 (chemical formula: CH2F2) refrigerant.
For heat-pump refrigeration systems using a refrigerant, since HCFC-base refrigerants having larger ozone-depleting coefficients have became a target of CFC regulation, an R410A (R32:R125=50:50) refrigerant that is an HFC-base refrigerant having an ozone-depleting coefficient of zero is in use as an alternative refrigerant therefore. As refrigeration systems using the R410A refrigerant, indeed those capable of obtaining COP (Coefficient Of Performance) levels equivalent to that of an R22 refrigerant have been developed into products, but further improvement in COP is desired from the recent years"" demand for energy saving. However, the R410A refrigerant has a problem that it cannot be improved in COP beyond the R22 refrigerant without increasing the size of the heat exchanger to thereby increase the amount of charged refrigerant with the resulting cost increased.
Therefore, an object of the present invention is to provide a refrigeration system capable of improving the COP while ensuring sufficient reliability by using a working medium containing an R32 refrigerant.
In order to achieve the above object, there is provided a refrigeration system which uses a working medium composed of an R32 refrigerant or a mixed refrigerant containing at least 70 wt % of the R32, and polyvinyl ether oil whose viscosity at 40xc2x0 C. is 46-82 cst.
The present applicant has discovered through experiments that a favorable lubricity of the compressor, a sufficient reliability, and a high COP can be obtained, while global environmental problems are provided for, by using for the refrigeration system a working medium which consists of the low-GWP (Global Warming Parameter) R32 refrigerant free from ozone layer depletion or a mixed refrigerant containing at least 70 wt % of R32, and polyvinyl ether oil whose viscosity at 40xc2x0 C. is 46-82 cst. Therefore, according to the refrigeration system having the above constitution, the COP of the system can be improved by lowering the viscosity at 40xc2x0 C. of the polyvinyl ether oil used as refrigeration oil for the R32 refrigerant within a range of 46-82 cst that allows sufficient reliability to be obtained, and thereby improving the mechanical efficiency of the compressor., Further, by selecting a polyvinyl ether oil whose viscosity at 40xc2x0 C. is low within the range of 46-82 cst as the refrigeration oil, the refrigeration system such as a split-type air conditioner having an indoor unit and an outdoor unit separately can be made larger in the high-low difference between the indoor unit and the outdoor unit, larger in the length of the connecting pipe that connects together the indoor unit and the outdoor unit, and further thinner in the diameter of the gas connecting pipe, as compared with systems using the R410A refrigerant or the R22 refrigerant.
In one embodiment of the present invention, the viscosity of the polyvinyl ether oil at 40xc2x0 C. is 46-68 cst.
According to this embodiment, the COP of the system can be improved more reliably.
In one embodiment of the present invention, a. winding of a stator of a motor for a compressor is coated with an insulating layer of at least one selected from among crosslinked-polyethylene, polyvinyl formal, polyester, polyesterimide, polyamide and polyamide imide.
According to the refrigeration system of the above embodiment, by coating the winding of the stator of the motor for the compressor with an insulating layer of at least one selected from among crosslinked-polyethylene, polyvinyl formal, polyester, polyesterimide, polyamide and polyamide imide, weather resistance of the insulating layer is improved, high reliability can be obtained, and long-term service can be achieved.
In one embodiment of the present invention, at least one among an antifoaming agent, a moisture supplemental agent or an extreme pressure additive is added to the polyvinyl ether oil.
According to the refrigeration system of the above embodiment, by adding an antifoaming agent to the polyvinyl ether oil, foamability can be suppressed, and seizure of the compressor caused by suction of the refrigerant due to a foaming phenomenon can be prevented. Further, by adding a moisture supplemental agent to the polyvinyl ether oil, degradation in chemical reaction caused by an effect of moisture and freezing in portions of low temperatures can be prevented. Further, by adding an extreme pressure additive to the polyvinyl ether oil, a chemical adsorption film is formed on the sliding surface of the compressor so that the lubricity of the slidable portion can be improved.
In one embodiment of the present invention, the refrigeration system comprises a refrigerant circuit in which a compressor, a condenser, a decompressor, and an evaporator are connected in a loop, the refrigerating cycle having no dryer for eliminating moisture in the refrigerant.
According to the refrigeration system of the above embodiment, by using the polyvinyl ether oil resistant to moisture and less in degradation for the refrigeration oil, the dryer can be eliminated, allowing a cost reduction and downsizing of the system to be achieved.
Also, there is provided an air conditioner using a working medium composed of an R32 refrigerant or a mixed refrigerant containing at least 70 wt % of the R32 and polyvinyl ether oil whose viscosity at 40xc2x0 C. is 46-82 cst,
wherein the air conditioner has an indoor unit and an outdoor unit.
According to the air conditioner having this constitution, the high-low difference between the indoor unit and the outdoor unit can be increased, the length of the connecting pipes can be increased, and further the diameter of the gas connecting pipes can be narrowed, as compared with air conditioners using the R410A refrigerant or the R22 refrigerant.